Strength and Stamina? Well Both men are essentially equal. Muscle size is irrelevant.

Reflex and reaction time? Well Both men are equal. Zod had to hone his senses for military and Clark had to do it every day of his life to not go fruit loops.

Because of this Zod has no advantage except actual technique.

Then Superman has the advantage of Flight. He's had some time to experiment and fight in a three dimensional space. Zod while he gained the ability is still 2D fighting/. In addition while Clark may not know his limits, he knows where they don't stop. Zod doesn't know how hard he can punch.

And of course Zod is on a suicide run. He's being sloppy. He wants to die.